This invention relates to a device for inspecting components and particularly to one using an array of light sources and photodetectors as a means of evaluating a component for conformance to spatial form criteria.
In this era of emphasis on high quality products, non-contact inspection systems are being used in large numbers. In order for a complex machine to operate as designed all of its sub-components must comply with quality criteria. In some manufacturing settings, 100% inspection of components parts is a requirement of the customer. For example, fasteners used in the automobile industry and elsewhere often must be individually inspected to determine if they meet spatial form and other criteria.
Numerous types of inspection systems are presently used. One general type uses contact probes which touch a component at various points and determines if its dimension or profile meets certain criteria. Contact devices however, have inherent limitations in that they are subject to wear and generally require that the component and the contact probe be accurately positioned during the evaluation process. Moreover, such devices are generally slow to operate and are limited in terms of the number of criteria and complexity of profiles which they can evaluate.
Various non-contact inspection systems are also known using various techniques. For example, ultrasonic inspection systems examine reflected sound waves as a means of characterizing a component. Various systems based on a video image of a part are also known. In addition, laser gauging systems are used in which specific dimensional measurements can be obtained.
In general, however, although known non-contact inspection systems are extremely useful, they have certain limitations. Many of the available non-contact gauging systems require complex data processing approaches which impose expensive hardware requirements and can limit the speed with which evaluations can be accomplished. Preferably, evaluation of a workpiece can be conducted in a rapid enough fashion that the parts can be directly sorted into qualified or disqualified part streams. Prior art systems also tend not to be easily adapted to various parts configurations or for evaluating different features of a part. Moreover, many of the currently available non-contact inspection systems have limitations in terms of the number of parameters which can be effectively examined during the inspection process. Another disadvantage of some known system is their limitations in terms of the types of parameters which can be considered. For example, often fine details of thread profiles of fasteners are needed. Moreover, many prior art systems, although performing adequately in a laboratory setting, are not sufficiently rugged for a production environment where temperature variations, dust, dirt, cutting fluids, etc. are encountered.
In accordance with this invention, a non-contact inspection system is provided which enables rapid inspection to be conducted permitting parts to be immediately sorted in terms of being in conformance or out of conformance with spatial form criteria. Moreover, a hard copy of part geometry can be generated pointing out specific form discrepancies, for example, for a threaded fastener, the diameter, length, profile and threads can be evaluated. In the case of the production of fasteners, the process often begins with wire stock which is fed into a cold heading or screw type forming machine. The part is die-formed or cut in a machine into a shape that may include several diameters and possibly a threaded or knurled length. The formed part may require secondary operations such as thread rolling, heat treating, plating etc. It is not uncommon for one or more of the processes to fail to produce the desired geometry of part. The occurrence of such defects is often not adequately monitored through random part selection or other quality assurance processes which do not provided 100% inspection. The inspection system of this invention is also highly adaptable for evaluating various components.
In the inspection system of the present invention, parts move by gravity or other means along a track through a test section. Initially, the part length is established through the use of a length detection array having a number of light sources and associated photodetectors. One of the sources generates a sheet of light oriented in the direction of travel of the part. The extent to which the sheet of light is blocked by the part is related to its length. In addition, the part passes through a profile detection array having one or more of light sources whose output is also in the configuration of a sheet of laser light oriented perpendicular to the part motion which cuts through the part as it moves past. Significantly, the evaluation of component length and profile in accordance with this invention is achieved through the use of single channel photodetectors. The use of single channel output photodetectors in accordance with this invention inherently provides advantages in terms of signal processing and data reduction.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.